UV-Curable Inkjet Polymer for Thermal Print Head Stability
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Solution Overview
Problem
Existing UV-curable inkjet ink compositions face challenges such as premature polymerization in thermal print heads, nozzle clogging, and safety hazards due to organic solvents and flammability, while also requiring improved water solubility and stability for functional patterning applications like electroless metal plating and sensor formation.
Innovation Solution
A UV-curable composition featuring a reactive polymer with at least 5 mol % pendant metal complexing water-solubilizing groups and crosslinking capabilities via [2+2] photocycloaddition, which is water-soluble before curing and becomes water-insoluble after, allowing for stable thermal ejection and UV curing without free radical initiators, and optionally includes humectants or surfactants for improved inkjet performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal DOD print heads are used for high-speed inkjet ejection, then print speed and ejection rate are improved, but the high temperature (300°C) decomposes or destabilizes the ink composition causing kogation and nozzle clogging
Solution Approach 1:
The patent changes the chemical composition parameters of the ink by incorporating thermally stable components that can withstand 300°C heating without decomposition. This includes using specific resins and curing agents that maintain stability at high temperatures, allowing thermal print head operation without kogation or clogging
Solution Approach 2:
The patent employs a curing agent that reacts rapidly during the thermal ejection process to form a stable crosslinked network. This disposable curing mechanism occurs quickly during printing, converting the unstable liquid ink into a stable cured structure that resists thermal degradation
2Reliability
If organic solvent-based UV-curable inks are used, then curing performance is improved, but health and safety hazards increase due to flammability and toxicity
Solution Approach 1:
The patent fundamentally changes the solvent parameter from organic to aqueous base. The ink composition uses water as the primary solvent with specific hydrophilic resins and curing agents that maintain UV curability. This parameter change eliminates flammability and reduces toxicity while preserving the crosslinking curing mechanism
Solution Approach 2:
The patent introduces water-soluble curing agents and photoinitiators as intermediaries that enable UV curing in an aqueous system. These intermediaries bridge the gap between water-based safety requirements and UV curability needs, allowing the ink to cure effectively without organic solvents
3Strength
If conventional UV-curable inks are used, then crosslinking capability is improved, but premature polymerization occurs in thermal print heads
Solution Approach 1:
The patent changes the photoinitiator parameters to use compounds with high activation energy that require UV light to trigger polymerization. These photoinitiators remain stable at thermal print head temperatures (300°C) but activate rapidly upon UV exposure, preventing premature curing during printing while maintaining strong crosslinking capability
Solution Approach 2:
The patent performs preliminary stabilization of the ink composition by selecting components that are thermally stable but UV-sensitive. The curing agents and photoinitiators are pre-configured to remain dormant during thermal printing, then activate in sequence when UV light is applied, ensuring crosslinking occurs only at the intended stage
4Adaptability or versatility
If piezoelectric DOD print heads are used, then tolerance to wide range of ink compositions is improved, but manufacturing cost and ejection time increase
Solution Approach 1:
The patent adjusts the ink viscosity and surface tension parameters to optimize for thermal ejection. By controlling these physical parameters through specific resin selections and concentrations, the ink achieves stable droplet formation and ejection at high speeds using thermal print heads, matching or exceeding piezoelectric performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a stable, water-soluble, and thermally stable UV-curable polymer that prevents premature polymerization and nozzle clogging, ensuring reliable inkjet printing and enabling the formation of high-resolution, electrically conductive patterns with enhanced antimicrobial properties.
Implementation Method 1
crosslinking capabilities via [2+2] photocycloaddition
Implementation Method 2
The resistive heating element typically reaches temperature of about 300° C. that can decompose or destabilize the ink jet ink composition and cause kogation (build-up of decomposition products on the heater surface or in the ink chamber) and eventual nozzle clogging or heater failure.
Data Source
AI summary
Articles are prepared with a substrate and an ink jetted and UV-curable image some of which also include metal nanoparticles or reducible metal ions. The in jetted and UV-curable image can be obtained from an ink jettable and UV-curable composition comprising: a reactive polymer comprising: (a1) or (a2) recurring units comprising pendant metal complexing water-solubilizing groups, (b) at least 5 mol % of recurring units comprising a pendant group capable of crosslinking via [2+2] photocycloaddition, and optionally (c) at least 1 mol % of recurring units comprising a pendant amide, hydroxyl, or lactam group, or a pendant precursor moiety for the pendant amide, hydroxyl, or lactam group. Such articles can be used to provide electrically-conductive articles and devices after electrolessly plating a complex of the metal nanoparticles and the UV-cured reactive polymer.